This invention relates generally to wire and cable strippers. More particularly this invention relates to a hand-held stripping tool for removing a sliver-like segment of the outer sheath from a flat multi-conductor cable. The stripper of the present invention is configured to longitudinally strip the sheath from a flat multi-conductor cable without damaging the underlying contents of the cable.
The stripping of cables is a common aspect of modifying, constructing, and maintaining electrical equipment and facilities. Common types of cables include multi-conductor cables such as "ROMEX" brand cable sold by General Cable Corporation for distributing power. These types of cables typically have three or more conductors protected in a sheath. At least two of the conductors are typically individually insulated in addition to having the protective sheath. Depending on the country and the application, the construction of these types of flat cables may vary slightly, but the overall constructions are quite similar.
When stripping flat multi-conductor cables, it is necessary to slit or strip the outer sheath to gain access to the interior contents and then strip the insulation from the individually insulated wires to expose the conductors. Regardless of the type of cable being prepared, it is desirable to slit or strip the outer sheath without damaging the underlying insulation or conductor.
There are a number of prior art tools and methods for accomplishing the stripping of the sheath of a flat multi-conductor cable. A common method is to use a pocketknife to slit the sheath along the longitudinal axis of the cable and then make a cut around the circumference to remove the severed portion of the sheath and expose the conductors. Although this method will suffices it has the potential of damaging the insulation on the individual conductors. Furthermore, physical injury to the party stripping the cable is also possible. To simplify the process of stripping these types of cables, many types of specialized tools have been developed and are well know in the art.
U.S. Pat. No. 4,951,393 to Wallace discloses a cable stripper especially adapted for stripping multi-conductor cable such as "ROMEX" brand cables. Wallace teaches a tool having a blade for slitting the outer sheath of the cable to a depth approximately equal to the thickness of the sheath material. The tool may further include a separate blade arrangement having a plurality of sharpened circular openings for stripping the insulation from the individual insulated wires. The tool disclosed by Wallace includes a guide for controlling the depth of the slit in the sheath. However variations in the thickness of the sheath, selection of different size cables, and variations in the pressure applied to the slitting blade during operation will result in a slit depth that is either slightly greater or less than the thickness of the sheath. A slitting depth slightly less than the sheath thickness will result in the sheath being difficult to remove and a slitting depth slightly greater than the sheath thickness can inadvertently damage the insulation on the individual insulated wires. Furthermore, the tool as taught by Wallace does not readily allow for longitudinal stripping long lengths of the insulation from insulated wires.
U.S. Pat. No. 5,535,519 to Brimmer also teaches a tool for stripping insulation from a cable. Brimmer teaches a tool that comprises a pair of handles similar to that of pliers. However, the handles operate a pair of jaws adapted for cutting insulation. Each jaw includes a series of semi-circular cutting edges that combine to form a series of circular openings when the jaws are in the closed position. Each jaw also carries non-circular cutting edges that combine to form a dumbbell-shaped opening when the jaws are in the closed position. The cutting edges are sharpened such that they can cut the insulation and allow it to be removed. The series of circular openings allow for round insulated wires of varying diameters to be stripped without appreciably damaging the conductor. The dumbbell-shaped opening is useful in stripping the outer sheath from cables such as "ROMEX" brand multi-conductor cables. The tool as taught by Brimmer does not readily allow for longitudinal slitting or stripping of insulation from conductors.
U.S. Pat. No. 5,325,593 to Chen teaches a double bladed vegetable peeler having pivotally mounted blades and guides similar to that contemplated for the present invention. As the disclosed and claimed utility of the peeler is for removing the skin from a vegetable or fruit, an element or elements for guiding the tool along the longitudinal axis of a wire or cable is not disclosed. Without such a guiding element or elements, the orientation of the wire or cable relative to the tool and the force applied between the blade and the wire or cable would not be controllable. This uncontrolled stripping operation would result in the strip depth and location of the insulation or sheath to be inconsistent, causing damage to an underlying insulation or conductor.
Accordingly, a need has arisen for a cable sheath stripping tool that overcomes the shortcomings of the prior techniques and tools. The tool disclosed herein strips the sheath from a flat multi-conductor cable along the longitudinal direction of the cable without damaging the underlying conductor or their insulation, if so insulated. The tool adjusts for sheaths having different thickness. Furthermore, the tool is constructed to slit to a depth approximately equal to the thickness of the sheath without significant skill of the user. For flat multi-conductor cables with three or more conductors in a sheath, the tool is configured to strip the sheath from adjacent the conductors at the edges of the cable as well as the sheath from adjacent at least one conductor positioned between the two outermost conductors.